# Outside Temp of a vessel is 40 Deg C and Water inside it is 86 Deg C.. Why?

#### rahulpsharma

Joined Sep 5, 2010
60
I was boiling water in a steel utensil.

Used Fluke's IR Gun (59 Max) to measure the temperature of Water inside AND the surface temp of vessel outside.

The boiling water read 86 Deg C whereas the outside surface temp of vessel read just 40 Deg C. Why is that?

If I touched the outside of the vessel it would 'feel' extremely hot but measurement shows just 40 Deg C. So what's going on here?

I tried changing the emissivity of the IR Gun but except for minor corrections, the outside temperature of this vessel containing boiling water always remained in the lows of 40s...!!

Most of the other things that I measured showed the temp in the right ballpark area... So what's going on with the Boiling Water System...!!

Rahul

#### crutschow

Joined Mar 14, 2008
34,457
I suspect the emissivity of the shiny metal is rather low.
Paint a patch of it with black paint (or even a black magic marker), and I think you will get a much closer temperature to the water in the container.

#### rahulpsharma

Joined Sep 5, 2010
60
I suspect the emissivity of the shiny metal is rather low.
Paint a patch of it with black paint (or even a black magic marker), and I think you will get a much closer temperature to the water in the container.
Awesome...!! Thank a lot for the right pointer...!!! It worked... ...!!

#### AlbertHall

Joined Jun 4, 2014
12,346
<nit pick mode>
If the water is at 86°C then it isn't boiling.
</nit pick mode>

#### MrChips

Joined Oct 2, 2009
30,821
There is something called “ black body radiation”.
@crutschow is right on the spot.

#### crutschow

Joined Mar 14, 2008
34,457
<nit pick mode>
If the water is at 86°C then it isn't boiling.
</nit pick mode>
The water likely also has an emissivity of less than 1.

#### ci139

Joined Jul 11, 2016
1,898

#### crutschow

Joined Mar 14, 2008
34,457
To make the kettle even more emissive, add a layer of carbon, such as from a candle flame against it for a few moments.
Carbon black has a very high emissivity.

#### joeyd999

Joined Jun 6, 2011
5,285
<nit pick mode>
If the water is at 86°C then it isn't boiling.
</nit pick mode>
It is if he's at 14,000 ft...

#### cmartinez

Joined Jan 17, 2007
8,257
It is if he's at 14,000 ft...
In fact, cooking a meal properly becomes tricky when one lives in a city above 6,000 ft sea level...

#### DickCappels

Joined Aug 21, 2008
10,185
In fact, cooking a meal properly becomes tricky when one lives in a city above 6,000 ft sea level...

#### atferrari

Joined Jan 6, 2004
4,771
<nit pick mode>
If the water is at 86°C then it isn't boiling.
</nit pick mode>
Maybe rahul lives well up there in Nepal, close to willem.

#### atferrari

Joined Jan 6, 2004
4,771
In fact, cooking a meal properly becomes tricky when one lives in a city above 6,000 ft sea level...
Pressure cookers to the rescue.